Various ramblings and musings on gardening, agriculture, food and related subjects.

Sunday, March 13, 2016

What really stresses me out - weeding

Its the end of the
winter and it has been very wet, and for the most part very mild. We
have a long growing season here in the Welsh borders anyway, and the
winter wet adds to the problem. A long growing season a problem? Yes,
because it means weed grasses, and a few other things, like creeping
buttercup, can just keep on growing continually, while the range of
perennials we want to grow, both garden and native species, are
dormant.

We have, in Britain, an
incredibly aggressive flora of species, basically grasses, that are
very effective at smothering the ground and most other non-woody
vegetation, which if left unchecked they eventually eliminate. It is
one reason why we don't have much of a problem with invasive alien
species, as they can never get a foothold. But who needs invasive
aliens when you've got invasive natives? They, and I basically mean
tillering and rapidly spreading grasses, can grow at low temperatures
and root very quickly into new ground. They are one reason for the
low floral diversity of much of the British countryside (the other
main one is the last Ice Age). In the garden they smother perennials,
rooting into the crown and establishing a canopy of foliage before
the perennial starts growing. This is also one of the reasons that so
much of the British countryside has very low floral diversity.

The result of all this
is that we, in the west of Britain, have a major problem dealing with
weedy grasses. A major problem. Our own plot has a fertile soil,
particularly rich in phosphorus, which grasses love, and it is quite
heavy, so getting weeds, fine-rooted grasses in particular, out, is
THE problem. I would say that weeding is our number one garden task,
in fact I would say that it is equal in time and effort to all the
other garden tasks combined. People who don't garden here probably have no conception of how problematic this is.

If I were a 'normal'
gardener I would be less ambitious, plant densely and be do a lot of
hand weeding. But because of my professional interest in researching
diverse low-maintenance plant mixes, I've got a lot of ground to
cover. I want to get a sense of how realistic it is for those who
work with minimal resources, such as in public spaces, can manage, so
I have to look at all weed control methods. And it is a conundrum.

Handweeding

In light soils this is
easy and basically can be regarded as solving the problem. Here on
our heavy soil it is every impractical until the soil dries out, as
you end up with a barrow full of clods of earth, it being impossible
to shake the soil off the roots.

Hoeing

'Traditional' garden
practice involved a lot of hoeing, which detaches weeds from the
soil, so they dry out and die on the surface. However, conventionally
it went hand in hand with having bare earth between plants, which
simply offers habitat to yet more weeds. I, like many other
'naturalistic' gardeners, aim at having as extensive a vegetation
canopy as possible, which is one of the most effective ways of
preventing weed growth. During the winter however, with most
perennials dormant, the native weedy grasses can move in, from any
seed left from plants which were not removed last summer. Hoeing
amongst established perennial clumps is not easy, often ineffective
and in our conditions weeds don't die on the soil surface unless we
have a dry east wind – they actually carry on growing and then
re-root!

Hoeing has many other
disadvantages. Too early in the year and if you make a mistake, you
decapitate a perennial. It is also quite destructive, of seedlings
of desired plants and of the whole layer just above the soil surface
- of decaying plant remains, mosses, small harmless creeping
spontaneous plants – this layer being an important invertebrate
habitat and therefore crucial for garden biodiversity. It, and hand
digging, also disturbs the soil, bringing up yet more seed seed.

Burning

The idea of burning is
an unorthodox one, but one which the prairie movement has introduced
us to. It is the oldest land management tool: a great many tribal
cultures around the world have used it to manipulate their
environments throughout history. Out in the country, where we are, it
is possible to cut down perennials, and then have a prairie burn with
the debris. Not really very sociable if you have neighbours! And not
legal in many places. The alternative is to rake off the debris,
compost it or use it as mulch elsewhere and then go over with a flame
gun.

Burning certainly
knocks back weed grasses, so they are forced to regrow and by the
time they do so, the perennials will coming on full stream. Burning
will kill seedling grasses and a lot of other early germinating weed
seedlings, such as goosegrass. However, if you have evergreen
perennials, very early emerging ones, or bulbs, it has to be done
very carefully.

Burning is a
particularly good and fun way to get rid of grass debris. Molinias
and Calamagrostis go up like fireworks, to the extent that if I were
a public park manager in some places I would think twice about
planting them. Miscanthus here does not dry out enough, although in
the US I am told it goes off like a bomb.

Taking a flame gun
solution to late winter weeds is a relatively new practice, widely
promoted as an alternative to handweeding/hoeing or using herbicide.
It is also increasingly being used in organic farming. It is of
course is not particularly sustainable, even less so than Roundup, as
propane gas is a fossil fuel. It, and prairie burning are also very
destructive for the same reasons as hoeing – goodbye desired
seedlings and ground level habitat. It also will not kill deeper
rooted perennial weeds, or indeed most weed grasses when established.
For persistent perennial weed grasses it is actually pretty useless.

Herbicide, i.e. Roundup

I am not organic (it
won't feed the world) and Roundup comes in very useful for the most
difficult places, or where I simply get to the end of my tether with
weedy grasses, and it is a fantastic time saver. It is non-persistent
and does have a good safety record, but we can never be sure, and
research may yet show something up which may mean we should consider
not using it. Many studies have been conducted over the years and it
has come out well on the safety front (though it should not be used
on sandy or stony soils which don't absorb it and allow it to be
broken down by bacteria, as happens on humus or clay rich soils, and
of course nowhere near water). Some recent studies have suggested it
may be a carcinogen, but the jury is still very much out.

There is a bigger
problem though, essentially a political one, as it is so impossible
to have a sensible discussion with many people about Roundup, as they
have made up their minds it is a creation of the devil, and that's
that. The organic movement is a dogma after all. But the fact that to
many people it is unacceptable is where we are at, so finding
alternatives is important, which makes me all the more interested in
researching a wide variety of non-chemical methods of weed control.

I think you could make
out a good case that Roundup is the least invasive method of weed
control, as it does not destroy the immediate above ground habitat,
leaves mosses untouched, and there is, as far as I am aware, no
evidence of a significant negative impact on animal biodiversity
(I've just been through a load of scientific papers on this). It,
like burning, also avoids disturbing the soil and so bringing up
buried weed seed. But convincing many domestic gardeners of this is
probably about as fruitless a task as persuading Donald Trump to
believe in climate change.

Before I leave the
subject of Roundup, if there is anyone still reading, I would like to
make a parallel with agronomy. The Americans have, for some time now,
been giving up ploughing, the practice that for many of us is somehow
synonymous with arable agriculture. Ploughing is very destructive of
soil structure, of soil life, and can encourage disastrous soil
erosion. It is for this latter reason that the US Department of
Agriculture has for some time now been encouraging 'no-til'. There
are other good reasons too, as not ploughing soil means that the soil
builds up its organic content, good for holding on to water,
nutrients and sequestering carbon. In fact no til is being promoted
as a major carbon dioxide sink, and therefore an important part of
controlling CO2 emissions. The idea is beginning to catch on with
British farmers too.

Trouble is no-til
classically involves spraying weeds off with the dreaded devil's milk
Roundup and then, a few weeks later sowing with a device which slices
through the dead weeds into the soil and sows the crop seed very
precisely. The alternative is a fossil fuel flame gun. There is no
easy answer here.

Strategies for the
future

Encourage ever denser
planting.

As more and more
species seed and spread my plantings are getting denser and therefore
more weed resistant. However there are some perennials which do seem
to be particularly prone to grass invasion of the crown and no amount
of dense planting will ever solve this if there is a local source of
weed grass seed.

Encourage ground level
perennials which will deny spaces to weeds but survive the
competition of the taller perennials.

Now this is a tall
order! Primula vulgaris, P. elatior, polyanthus and other hybrid
primroses are actually pretty good at this as they are more or less
summer dormant and do most of their growth in the October to April
period when the the heat-requiring summer perennials are dormant.
Liriope too, but in our cool summer climate this spreads so slowly as
to be almost useless. There is not a lot else.

Plant a matrix of weed
suppressing evergreen ground cover and then grow taller perennials in
it.

I tried this with the
evergreen Carex glauca, and it was a total failure, as all sort of
weeds from grasses to seedling Geranium 'Claridge Druce' moved in and
took over. I'm now trying it with Phlomis russeliana which here is
our most effective weed-suppressing perennial but which has
co-existed well with several robust perennials for five years in some
research plots. Any more suggestions?

Re-define what a weed
is

This can be very
fruitful. I have never understood why some people get so het up about
lesser celendine which spreads like mad, flowers in March and then
goes dormant. What problem is that? Creeping buttercup may be a pain
but in with established taller perennials it soon gets overshadowed
and can then be appreciated as a nice spring wildflower. I am
debating about whether to leave it some of my research plots.

At the end of the day a
weed is something which has the ability to out-compete and therefore
destroy the plants we are trying to grow.

Use slow-to-decay mulch

This is what I am
intending to do with those parts of the garden which are not research
plots, where decorative impact is important and where weed grasses
have been a particular problem. Many mulches simply rot down too
quickly but council green waste seems to be much longer lasting,
possibly because it is composted at a high temperature and is
therefore almost charcoal like (on the way to being bio-char
perhaps?). Weeds pull of out it nice and easy. So the plan is, buy a
lorry load, and get it spread, creating a new and much more friable
surface for weed control.

I think this weed grass
control issue is so important, I'll do an annual update. Now, for
having even mentioned the possibility of using Roundup, I'll sit back
and wait for the death threats.

16 comments:

Oriental poppies also fulfil the criterion of growing fast in early spring and outpacing weeds - clumps here have substantial leaf growth by early March. Same goes for Hemerocallis. Otherwise I can think of many perennials that power their way up through a covering of weeds quite happily here, including Aquilegias, Thalictrum aquilegiifolium, Crambe cordifolia, Acanthus, Actaea simplex, Japanese anemones, Cephalaria gigantea, Helianthus sp. to name a few. Our soil is much lighter than yours, so these might not do so well for you, but if Phlomis russeliana is fine, I'd have thought these would be too.

PS - I choose not to use Roundup, partly on the precautionary principle but mainly because it doesn't remove the weeds straight away the way that hand weeding does. But we're on light soil and hand weeding is a breeze - almost enjoyable on a sunny spring morning.

I'm sorry to read about your struggle with weedy grasses, Noel. It sounds like you are trying a variety of methods to combat them, and I wish you luck in discovering what works best in each area. I too don't shrink from the use of Roundup when appropriate, as some perennial weeds are simply impossible to deal with effectively in any other manner. Yes, it's wise to avoid chemicals whenever possible, but human effort is worth something and shouldn't be wasted on futile tasks (like trying to dig out a bed full of creeping charlie, etc.). Thanks for sharing your level-headed approach with us. Best, -Beth

Mulch is our best strategy. Added to that - we plant a lot of bulbs between the perennials (mostly C. tommasianus, wintergreen Cyclamen coum) - they take most of the space, weeds would like. Besides it looks great in early spring. We mulch with compost and on top we give small lava pebbles or other non-organic mulch. Helps a lot. I look forward to your next episode on this very interesting topic! Greetings from munich - Renate

This is a really interesting discussion of a critical management aspect of all gardens. Sympathising with your struggles as gardeners in an even wetter and more western part of the UK, I think you rationally cover all bases. A couple of comments - we have used, and I suspect will again use glyphosate, as weed knockout, in awkward places/tricky to hoik out weeds, BUT do beware - we both suffer a range of flu like symptoms (achy joints, fatigue, etc.) 4 to 5 days after using it, unless we are really, really careful to mimimise respiratory exposure...and I'm always wary of how anything like this which pretty much kills all green leaved plants, except maybe mosses, might affect mammalian (including our own) cells.So we hand weed, and try as quickly as possible to get total low ground cover. We love moss for this role - its easy in our climate, as a base layer, and then add in ground huggers, with preferably insect friendly flowers - including mossy saxifrages, purple bugle, native germander speedwell, a Chinese creeper which is brilliant in all but very dry shade - Chrysoplenium davidianum, and variants on London Pride , Saxifrage urbium. Patch planted, once you have this ground cover, taller perennials can grow through and cope with these base layers, as well as many of the spring bulbs. So this is a time consuming set up, though economical to set up early few years. You do still get fine grasses growing, particularly if you disturb the base layer with, say, further bulb planting, but it's vastly reduced and just about manageable. For now!Eventually of course the weeds will win.And the snowdrops are about the only thing which will survive,as pointers that this was once a much loved garden, once we shuffle off!

Every year I battle weeds that encroach from neighbors yards. Am surprised you would recommend Roundup, toxic to most wildlife and a potential carcinogen. That said, I have on rare occasion used a similar product on certain thick invasive vines that cannot be pulled up. Once I cut the vine, I spray directly onto or carefully pour directly on the cut end where the vine continues into the ground. Everything else I pull up by hand.

Laying plastic or several layers of newspaper topped with mulch or soil around plants also helps control weeds.

Since stopping Roundup I now have toads, a snake once in a while, newts and salamanders. All these chemicals & fertilizers are very bad for our ecosystems. I'm in SE, PA.

After years of easy gardening and weeding in the dutch clay, we moved to the wetlands in New York State, were we immediately were faced by an army of deer and invasives. A combination so strong that all of our new neighbors had long ago given up the fight. The last desperate garden feature here is a densely knitted carpet of pachysandra. A plant that is on the list to become considered invasive as well.After trying most of your comprehensive list of weeding tactics, I planted, piece by piece, two acres (!)with lamium, which smothers out the weeds, and in contrast to pachysandra is easy to remove and replace. My garden today is filled with flowering plants, the lamium almost gone, something everybody, including myself, had considered impossible.I wish you luck with the task of weeding on the other side of the ocean, but please consider yourself lucky with all the garden knowledge around you and all the lovely available plants that do want to grow in the spots you have cleaned for them.I had so little help here, that I had to look for inspiration at what Piet Oudhof did, miles away in New York city, or read garden blogs from the English country side, to find ideas and solutions for this local problem.

I'll offer support instead of death threats for your use of glyphosate. There are plenty of habitat restoration projects in the States that wouldn't be possible if it weren't for glyphosate. I would rather see the careful and timely use of glyphosate than the rampant weedy landscapes that are left to seed because they overwhelm their owners.

This certainly is a familiar story to me. I'm continuously searching for ground covers that will, if not eliminate this problem, at least make it easier to deal with. The worst offenders here in my western New Jersey garden are European pasture grasses brought over long ago, by the early colonists I suppose. They are, as you say, evergreen, even in our very inhospitable winters. I try to control them by hand pulling new shoots in spring and judicious use of Roundup. These European grasses are particularly effective at invading the crowns of Panicum and Hemerocallis in my environment, but they can't invade the tight crowns of Miscanthus, which I have to use in place of Panicums, and they simply can't compete with the extremely large perennials I grow. But each spring, I'm amazed to see these green grasses thriving happily after I've cut and burned everything else.

Good to see you making a case for glyphosate - any reader of my blog will know i am an advocate of its use.What's this about not using on sandy soil?. Rubbish. My garden is very sandy but because of my methods and the minimum cultivation methods made possible by glyphosate its organic matter is extremely high. No problem with bacterial breakdown! Using glyphosate I have no problem with grassy weed whatsoever.PS there are several very good and very scientifically based gardeners in our village on the same sandy soil and they all use glyphosate

What about preemergent herbicides, such as corn gluten? Of course you wouldn't put it on a bed where you want certain seeds to grow, but in many gardens it can be appropriate. Do you have any experience to know how effective it is?

It is rare for me to sit down and read a blog which uses a lot of words. I don't have the time with a large garden that I garden single handed. But, I read right through to the end even when you thought you had lost some readers. I had watched a Monty Don program with a similar theme. Establishing a wildflower meadow, in which he talked about the grass thug. He used yellow rattle which he said invades the roots of the grass weakening it. I don't know if we have a similar plant here in Texas- I do know that Indian paintbrush invades the roots of other plants, and maybe this would do the same job. The reason for my interest is that I have a large septic spray field which I have tried for years to turn into a wildflower meadow. In the beginning I provided the company who came to over seed the disturbed ground with a mix of Texas wildflowers. My request was completely ignored and I found the full bags languishing by the garage. Of course there was Bermuda in their empty tanks. SInce then other grasses and weeds have come in and these grow during the winter season. I cannot establish a spring wildflower meadow and have just about given up. Maybe I should try an experimental area, scalped and torched and rounded up and see how that goes. For now my husband has said we should just mow and that I have enough to do in my enclosed gardens. All my gardening friends have closed minds to Round Up. I have to admit to them that I will use it when I need to. Some things you just can't fight.

I have a 2 acre garden open to the public all year around, so it has to be kept in reasonable contition all the time. We have a very heavy, very rich clay soil and almost all year around moisture, as you would expect in Ireland. As a professional gardener, having done my time over the years trying to put manners on out of control gardens, I take a very tough, zero tolerance line on weeds, as I have seen the effects time and time again of turning a blind eye on the problem until it's almost to late. Creeping buttercup, field vetch, rosebay willowherb, other willowherbs, and the various grasses, particularly annual meadow grass, must be kept in strong check. In particular, field vetch and rosebay willowherb must alway be totally removed. Scutch grass, of course, is no longer the scurge it once was thanks to Roundup. I say to the anti Roundup people: go get your teeth drilled the 'chemical' free 'organic' way, or get the dentist to use a homeopathic anastetic, oh, I see, you only have a problem with certain chemicals. The anti Roundup people remind me of the good townsfolk in the Western who promise to give the man a fair trial and then hang him. There is no talking to these people.Anway, as our gardens are maintained on a shoestring, we use a mixture of chemical (Roundup), some hand weeding, and everything is mulched with mini chip bark. (we rarely hoe as its a complete waste of time on heavy wet soils) It's not that expensive, (we do though get a good trade price, as we sell bark mulch in our garden centre in front of our gardens) compared to manhours saved and it lasts for up to 4 years. We top up when it gets a bit light on the beds but not as much is needed second time round. Very few weeds will germinate seeds in it, and when they do they are easily removed. We've tried the much cheaper council recycled mulches and found them worse than useless and a great seed bed for anything and everything. Composted bark is also useless except as a weed seed bed, though it looks nice.We've found that the majority of plants have absolutely no problem growing through the mulch, in fact we get good growth rates on most of our plants. We even have to Chelsea chop our solidagos to keep them from flopping.Anyway, in the wet mild British Isles the only really true naturalistic scenes are those made up primerally of trees and other woody plants. All else is just pushing the boulder uphill.

I have a 2 acre garden open to the public all year around, so it has to be kept in reasonable contition all the time. We have a very heavy, very rich clay soil and almost all year around moisture, as you would expect in Ireland. As a professional gardener, having done my time over the years trying to put manners on out of control gardens, I take a very tough, zero tolerance line on weeds, as I have seen the effects time and time again of turning a blind eye on the problem until it's almost to late. Creeping buttercup, field vetch, rosebay willowherb, other willowherbs, and the various grasses, particularly annual meadow grass, must be kept in strong check. In particular, field vetch and rosebay willowherb must alway be totally removed. Scutch grass, of course, is no longer the scurge it once was thanks to Roundup. I say to the anti Roundup people: go get your teeth drilled the 'chemical' free 'organic' way, or get the dentist to use a homeopathic anastetic, oh, I see, you only have a problem with certain chemicals. The anti Roundup people remind me of the good townsfolk in the Western who promise to give the man a fair trial and then hang him. There is no talking to these people.Anway, as our gardens are maintained on a shoestring, we use a mixture of chemical (Roundup), some hand weeding, and everything is mulched with mini chip bark. (we rarely hoe as its a complete waste of time on heavy wet soils) It's not that expensive, (we do though get a good trade price, as we sell bark mulch in our garden centre in front of our gardens) compared to manhours saved and it lasts for up to 4 years. We top up when it gets a bit light on the beds but not as much is needed second time round. Very few weeds will germinate seeds in it, and when they do they are easily removed. We've tried the much cheaper council recycled mulches and found them worse than useless and a great seed bed for anything and everything. Composted bark is also useless except as a weed seed bed, though it looks nice.We've found that the majority of plants have absolutely no problem growing through the mulch, in fact we get good growth rates on most of our plants. We even have to Chelsea chop our solidagos to keep them from flopping.Anyway, in the wet mild British Isles the only really true naturalistic scenes are those made up primerally of trees and other woody plants. All else is just pushing the boulder uphill.

I started each new area of the garden by clearing it with Roundup and mulching with bark chips - very effective. Perhaps one reason I have never had a bad weed problem. But also I am a fanatic handweeder. I enjoy pulling seedlings and looking for precious babies. I almost never let a weed get big enough to retain a clod of earth so it always seems easy. If you are always on top of the problem it is almost no problem. Wet springs make it more difficult of course. Hand weeding not really a low maintenance solution, but a light maintenace solution, little and often, every week

Otherwise I only use Roundup if I absolutely have to (bindweed for example). I dont have your problem with evergreen grasses, I wonder why?

But how to add compost if using a bark mulch? Now I only mulch with compost (having a nursery means I have more compost than I know what to do with, I know it is a luxury). Compost sometimes gives me much more hand weeding early in the year (depends on the weather when it is spread I think), millions of tiny seedlings, but they are very easy to pull up and after a month or so no more problem. My soil is unbelievably looser and more friable than it was 20 years ago

I haven't found a solution to weeds yet, and as much as I try to stay away from chemicals, I am not dogmatic about it. However, I want to add one point to the Roundup discussion. I live in an area of the US midwest where certain weeds started to develop a resistance to Roundup. That is one reason why I use it very sparingly and only in combination with other weed control techniques, to not further increase that problem. Here this product is widely overused by agriculture as well as home gardeners.

About Me

Garden writer and researcher, lecturer and teacher, based in the England/Wales border region. An occasional designer of plantings for gardens and public spaces.Other interests, and subjects for occasional publication are agriculture, food politics and environmental issues. Chiefly known for promoting naturalistic and sustainable planting design, I am a believer in design and decision-making based on science and evidence – so I have not signed up to organic jihad. And - lot of globe-trotting doesn’t stop me gardening myself either!
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This blog is a place for observations, thoughts and opinions that occur to me as a gardener, horticultural journalist, researcher and commentator on the garden and landscape scene. And sometimes on the food and agriculture scene too.... when, you should be warned, I sometimes express unfashionable thoughts.

PLANT SELECTION: LEARNING FROM NATURE

The first in a series of e-books I'm planning with My Garden School

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I am now publishing e-books through Amazon, for Kindle, smartphones, iPads etc. There are currently three available, two based on collections of writings for Hortus magazine, from the early 2000s, and one which is an interview with Beth Chatto. Click here for Amazon North America or Amazon UK.

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Interview

In February I went to Switzerland to do a lecture for the Swiss Hardy Plant Society (rather quaintly called the Swiss Friends of Perennial Plants). Here is the original English version of an interview he did with me. (you can see German and French above). Merci à Xavier Allemann.